Turbine component pattern forming method

ABSTRACT

A method of forming a pattern comprising a plurality of recesses within a turbine component is disclosed. The method includes simultaneously dissolving a plurality of portions of a selected section of the turbine component, thereby defining the plurality of recesses of the pattern.

BACKGROUND OF THE INVENTION

The present disclosure relates generally to material removal processes,more specifically to a method for incorporating a pattern within acoating deposited upon a substrate, and even more specifically to thesubstrate being a turbine component, more specifically an airfoilshroud.

In a gas turbine engine, such as may be used for electrical powergeneration for example, in order to achieve enhanced engine efficiency,it is important that the buckets rotate within a turbine casing or“shroud” with reduced interference to provide the enhanced efficiencyrelative to the amount of energy available from an expanding workingfluid. Typically, increased operation efficiencies can be achieved bymaintaining a reduced threshold clearance between the shroud and tips ofthe buckets, which prevents unwanted “leakage” of hot gas over tips ofthe buckets. Increased clearances lead to leakage problems and causesignificant reduction in overall efficiency of the turbine. However, itshould be appreciated that a reduction in clearances that leads tointerference between bucket tips and the shroud is generallyundesirable.

The need to maintain adequate clearance without significant loss ofefficiency is made more difficult by the fact that as the turbinetransitions to steady state operating temperature, different componentsthat possess varying thermal expansion properties can expand atdifferent rates. Furthermore, as the turbine rotates, centrifugal forcesacting on the turbine components can cause the buckets to expand in anoutward direction toward the shroud, particularly when influenced byhigh operating temperatures. Thus, it is important to establish reducedeffective running clearances between the shroud and bucket tips whilepreventing interference at various operating conditions of the turbine.

Typically, the shrouds are fabricated (for example, by casting andmachining) to include a concave profile that mates with a convex contourof a surface of the bucket tips (the rotation of the bucket tip forms aconvex contour towards the shroud, though it should be appreciated thatthe surface of each bucket tip is not necessarily convex, and may beflat). Mating the concavely machined shroud with the convex bucket tipcontour in this manner maintains a reduced clearance over the wholesurface of the tip. The shrouds often further include coatings such asthermally sprayed MCrAlYs where M is the base metal, Cr is chromium, Alis aluminum, and Y is yttrium, or aluminides for example, to resistoxidation and corrosion of the shroud in the high operating temperaturesof the turbine. It has been found that incorporating a pattern withinthe coatings increases the surface area and reduces airflow between thebucket and the shroud to perform in the same manner as a reduction inclearance between the bucket and the shroud, thereby increasingoperating efficiency. One current method to incorporate the pattern isto spray the coating onto the base of the shroud in conjunction with amask that reflects the desired pattern. Such spray masking methods areslow and have pattern geometry resolution limits. Another method toincorporate the pattern including the concave profile, or any desiredprofile, is conventional machining, such as computer numerical control(CNC) milling for example. Because of properties of theoxidation-resistant coatings, machining the coatings into the largesurface area of the shroud is difficult, and time and labor intensive.For example, each depression or recess of the pattern is formed in aserial fashion, one after another. Furthermore, the size and surfacegeometry of the pattern may be limited by that of the machining tool.Accordingly, there is a need in the art for an arrangement toincorporate patterns into turbine component surfaces that overcomesthese drawbacks.

BRIEF DESCRIPTION OF THE INVENTION

An embodiment of the invention includes a method of forming a patterncomprising a plurality of recesses within a turbine component. Themethod includes simultaneously dissolving a plurality of portions of aselected section of the turbine component, thereby defining theplurality of recesses of the pattern.

Another embodiment of the invention includes a method of forming apattern comprising a plurality of recesses within a coating disposedupon a turbine component. The method includes simultaneously dissolvinga plurality of portions of the coating disposed upon a selected sectionof the turbine component, thereby defining the plurality of recesses ofthe pattern.

These and other advantages and features will be more readily understoodfrom the following detailed description of preferred embodiments of theinvention that is provided in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring to the exemplary drawings wherein like elements are numberedalike in the accompanying Figures:

FIG. 1 depicts a perspective view of an airfoil shroud section inaccordance with an embodiment of the invention;

FIG. 2 depicts a cross section view of an airfoil shroud section inaccordance with an embodiment of the invention;

FIG. 3 depicts a schematic diagram of an electrochemical machiningsystem in accordance with an embodiment of the invention;

FIG. 4 depicts an embodiment of a used airfoil shroud section inaccordance with an embodiment of the invention; and

FIG. 5 depicts a flowchart of process steps for forming a pattern withina coating of the airfoil shroud section in accordance with an embodimentof the invention.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of the invention provides a process to incorporate apattern having a plurality of recesses into a surface of a coating, suchas the thermally sprayed MCrAlY coating or aluminides, to resistoxidation and corrosion for example, deposited upon a section of anairfoil shroud. Such coatings typically include elements from the groupof Nickel, Cobalt, Chromium, Aluminum, Yttrium, Rhenium, Rhodium,Ruthenium, Palladium, Platinum, Niobium, Molybdenum, Silicon, Hafnium,Iron, Manganese, and at least one from lanthanide series such asGadolinium, and Lanthanum, for example. In an embodiment, a chemicaletch is used to simultaneously remove the plurality of recesses fromselected portions of the coating to provide the desired pattern. As usedherein the term “portion”, used with respect to the oxidation resistantcoating, shall indicate a fraction of an area of the surface that isgreater than zero, but less than the entire area. In another embodiment,electrochemical machining (ECM) is utilized to simultaneously remove theplurality of recesses selected portions of the coating to provide thedesired pattern. While the embodiment described herein depicts anairfoil shroud as an exemplary substrate, it will be appreciated thatthe disclosed invention is also applicable to other substrates orturbine components that may incorporate difficult to machine coatings,such as on turbine buckets, nozzles, liners, and transition pieces forexample.

Referring now to FIG. 1, a schematic perspective view of turbinecomponent 50, such as an airfoil shroud section is depicted. The airfoilshroud section 50 includes a substrate 54, or base and a coating 58,such as the MCrAlY or aluminides coating, for example. The coating 58includes a pattern 62 disposed upon a surface 64 to face the buckettips. The pattern 62 influences airflow between the coating 58 and abucket (not shown) to perform in a same manner as a reduced operatingclearance between the bucket and the shroud section 50. Accordingly,incorporation of the pattern 62 into the coating 58 of the shroudsection 50 increases an overall efficiency of the turbine. The pattern62 includes a plurality of recesses 66, a plurality of protrusions 70,and a concave curvature 74. At least one of the base 54 and the coating58 include geometry of the concave curvature 74. Forming of the pattern62 begins with designing the desired pattern 62, including a geometry ofeach recess 66 and protrusion 70. In an exemplary embodiment of theshroud section 50, the recess 66 has a depth 75 greater than or equal toapproximately 0.25 millimeters (mm) (0.010 inches) and less than orequal to approximately 2 mm (0.080 inches) and a width 76 greater thanor equal to approximately 2.5 mm (0.100) and less than or equal to 5 mm(0.200 inches), with a protrusion 70 width 77 greater than or equal toapproximately 0.75 mm (0.030 inches) and less than or equal to 4.6 mm(0.181 inches). It will be appreciated that curvature 74 of the patternincreases a chordal width of at least one of the recess 66 andprotrusion 70. The foregoing is for purposes of illustration, and notlimitation.

In one process known as chemical etching, an etchant, such as one ormore of hydrofluoric acid, sulfuric acid, nitric acid, and combinationsthereof, for example, is selected, based upon a composition of thecoating 58, to dissolve the coating 58. FIG. 2 depicts a cross sectionof the base 54, the coating 58 and a mask 78 selectively disposed, orapplied upon the coating 58 prior to forming the pattern 62 within thecoating 58. A material of the mask 78 is selected that is chemicallyresistant to the etchant, that is, the etchant does not dissolve themask 78. Accordingly, portions of the coating 58 upon which the mask 78is selectively disposed will not be dissolved. Therefore, the etchant,in conjunction with the mask 78, will etch or dissolve portions of thecoating 58 (absent the mask 78) to provide the recesses 66 of thepattern 62. Accordingly, following dissolving of the portions of thecoating 58 to provide the recesses 66, the portions of the coating 58upon which the mask 78 is disposed are not dissolved, and therebyprovide the protrusions 70 of the pattern 62. Chemical etching removesmaterial to form the plurality of recesses 66 of the pattern 62simultaneously, in a parallel manner that reduces overall process timeas compared to machining each single recess 66 one at a time, therebylowering a production cost of the airfoil shroud section. It iscontemplated that for a typical airfoil shroud section 50, etching ofthe recesses 66 can be accomplished in cycle times of approximately 2 to3 minutes, as compared to multiple hours of CNC machining. It is alsocontemplated that multiple airfoil shroud sections 50 can be processedsimultaneously, further increasing a productive throughput of chemicaletching. A resolution, or geometric dimensional accuracy of chemicaletching is a function of etching depth. In an embodiment of chemicaletching, wherein depth to width ratios are about one to one, chemicaletching is contemplated to provide features, such as recesses 66 andprotrusions 70 having resolutions of approximately 0.127 mm (0.005inches).

In an exemplary embodiment, the mask 78 comprises a photoresistant mask78 that is applied directly to portions of the surface 64 of the coating58 via a lithography process, for example. For example, the surface 64of the coating 58 is cleaned, with a cleaner such as one or more ofacetone and isopropyl alcohol solvent followed by a rinse with deionizedwater. Additional lithographic solvents and a plasma etch prepare thesurface 64 of the coating 58 for application of a photoresistantmaterial. A mask or cover 82 is disposed between an energy source 86 andthe photoresistant material applied to the coating 58. The mask 82includes a geometry inverse to that desired of the mask 78. As anexample of inverse geometry, the mask 82 includes openings 84 thatcorrespond to the geometry of the mask 78 and allow transmission of theenergy created by the energy source 86. The remainder of the mask 82blocks transmission of energy, such as ultraviolet energy for example,from the energy source 86 to the photoresistant material. In response toexposure of the energy, the photoresistant material cures and adheres tothe coating 58. Solvents, and optionally, a second plasma etch, removeportions of the photoresistant material that have not cured, and thecured photoresistant material thereby defines the mask 78, which definesthe plurality of protrusions 70. In an alternate embodiment, use of themask 82 is replaced with a directed energy source, such as a laser beamfor example, that focuses the energy to the portions of thephotoresistant material that represent the desired geometry of the mask78. Use of the lithography process provides the mask 78 having geometryresolution as fine as 10 microns. Photoresistant materials are selectedbased upon their ability to chemically resist the etchant and therebyprevent dissolving of the coating 58.

In another embodiment, the mask 78 is produced by an additivemanufacturing process known in the art as direct writing. As withlithography, the direct writing process begins with cleaning the surfaceof the coating 58. An appropriate mask 78 material that is compatiblewith the direct writing process, such as particles suspended within aliquid or fluid medium for example, is selected. As with lithography,the mask 78 material selected must adhere appropriately to the coating58, and be chemically resistant to the etchant. The selected maskmaterial is applied directly upon the coating 58, using a suitabledirect write tool, such as a pen dispensing tool, a thermal plasma gun,laser transfer, or an ink-jet to deposit the suitable material upon thecoating 58, or a laser beam to cause the particles suspended in themedium proximate the coating 58 to locally activate and adhere to thecoating 58, for example. The direct write tool is guided, via roboticguidance for example, to apply the mask 78 material in accordance with adesired geometry of the mask 78, as may be provided via a computergenerated model, for example. The direct writing process furtherincludes consolidating or curing the mask 78 material applied to thecoating 58 via a curing activator appropriate to the selected material,such as one of heat energy, laser energy, plasma energy, electron beamenergy, ion beam energy, and combinations thereof.

It will be appreciated that the etchants described above to dissolve thecoating 58 are extremely corrosive materials, use of which requirespecialized handling procedures, and may therefore be desired to beavoided. Referring now to FIG. 3, a schematic diagram of anelectrochemical machining (ECM) system 90 to incorporate the pattern 62into the coating 58 of the airfoil shroud section 50 is depicted. Thesystem 90 includes a power source 94, a tool 102 and an electrolyte 98disposed between the coating 58 and the tool 102. As with chemicaletching, electrochemical machining selectively dissolves the coating 58and forms the plurality of recesses 66 (and protrusions 70) of thepattern 62 simultaneously, in a parallel manner that dramaticallyreduces overall process time as compared to machining each single recess66 one at a time, thereby lowering an overall production cost of theairfoil shroud section 50. It is contemplated that for a typical airfoilshroud section 50, electrochemical machining of the recesses 62 can beaccomplished in cycle times of approximately 2 to 3 minutes, as comparedto multiple hours of CNC machining. It is also contemplated thatmultiple airfoil shroud sections 50 can be processed simultaneously,further increasing a productive throughput of the ECM system 90.

In an embodiment, the power source 94 is a direct current (DC) powersource with the coating 58 in power connection with a positive terminal106 of the power source 94, either directly or via the base 54. The tool102 is in power connection with a negative terminal 110 of the powersource 94. Accordingly, the coating 58 and the tool 102 representelectrodes, such as an anode and a cathode respectively, of anelectrochemical cell, as will be appreciated by one of skill in the art.In response to the application of an electrical potential from the powersource 94, current flow or electrical charges passing through thecoating 58, via the electrolyte 98 will result in the dissolving of theanode (coating 58). It will be appreciated that a gap 112 is disposedbetween the coating 58 and the tool 102, such that any current flowoccurs through the electrolyte 98, not via contact of the tool 102 withthe coating 58. The application of power may be straight DC, or pulsedDC. In an embodiment, the coating 58 includes oxides and metal and thepulsed DC power includes alternating cathodic and anodic biased pulsesto preferentially dissolve oxides during one cycle and metal during theother. Power settings such as total machining time, pulse amplitude,pulse on-time, and pulse off-time will determine collectively the totalelectrical charges passing through the machining areas, which in turndetermine the amount of material removal, and therefore, the geometry ofthe recesses 66.

Because of the use of the power supply 94 to electrochemically dissolvethe coating 58 material, the electrolyte 98 of the ECM system 90 is lesscorrosive than the etchants described above, and therefore requires lessspecialized handling procedures. The specific electrolyte 98 to be usedis related to the material composition of the coating 58 to bedissolved. For example, hydrofluoric silicate, ammonium fluorosilicate((NH4)2SiF6), fluorosilic acid (H2SiF6), and aqueous solutions of sodiumchloride (NaCl), sodium nitrate (NaNO3), and sodium bromide (NaBr), andcombinations thereof are examples of such electrolytes 98 that are lesscorrosive than the etchants described above and are contemplated asappropriate for dissolving coatings 58 applied to airfoil shroudsections 50. While an embodiment is depicted having the tool 102 and theshroud section 50 immersed in the electrolyte 98, it will be appreciatedthat the scope of the invention is not so limited, and that theinvention will also apply to other means to dispose the electrolyte 98between the tool 102 and the coating 58, such as to use any of gaskets,pumps, and directed flow nozzles to provide and circulate theelectrolyte 98, for example.

In one embodiment, the tool 102 includes an inverse of the geometry ofthe desired pattern 62 to be formed within the coating 58. As an exampleof inverse geometry, the tool 102 includes protrusions 111 that aredisposed to correspond to the desired location of the recesses 66 of thepattern 62 in the airfoil shroud section 50 (best seen with reference toFIG. 1). Because the protrusions 111 are located closer to the coating58 than other portions of the tool 102, an increased current density (orcharge flow) results between the protrusions 110 of the tool and thecoating 58. The increased charge flow results in an increased localizeddissolving of the coating 58 that corresponds to the location of theprotrusions 111, thereby providing the recesses 66 of the pattern 62.Use of the tool 102 including the inverse of the desired pattern iscontemplated to provide pattern 62 features, such as the recesses 66 andprotrusions 70 having a resolution of approximately greater than orequal to approximately 0.13 mm (0.005 inches) and less than or equal toapproximately 0.25 mm (0.010 inches).

In another embodiment, the mask 78 is disposed upon the coating 58. Themask 78, for use in conjunction with the ECM system 90, shall beelectrically insulating to prevent current flow between the tool 102 andthe locations of the coating 58 upon which the mask 78 is disposed,thereby preventing dissolving of the coating 58 and providing theprotrusions 70 of the pattern 62. The mask 78 can be applied to thecoating 58 via one of the lithographic processes and the direct writeprocess, as described above. It will be appreciated that use of the mask78 in conjunction with the electrolyte 98 of the ECM system 90 (ascompared to the etchants described above) represents a less corrosiveenvironment to which the mask 78 is exposed. Therefore, use of the ECMsystem 90 allows selection of mask 78 materials suitable for use inconjunction with less corrosive environments. In an embodiment, thegeometry of mask 78 is produced separately, such as upon a polyestersubstrate for example, and subsequently disposed upon or transferred tothe coating 58. As a result of use of the mask 78, a finer resolution ofthe features of the pattern 62, is contemplated, such as the recesses 66and protrusions 70 having a resolution of greater than or equal toapproximately 0.13 mm (0.005 inches) and less than or equal toapproximately 0.25 mm (0.010 inches). In conjunction with the mask 78,the tool 102 need not include geometry that is the inverse of thedesired pattern 62, as the electrical insulation of the mask 78 preventsdissolving of the coating 58, to provide the protrusions 70.

Referring now to FIG. 4, an embodiment of a used airfoil shroud section50 is depicted. Use of the airfoil shroud sections 50 may result in wearof the protrusions 70 of the pattern 62. A worn geometry of theprotrusions 114 is depicted in solid lines, with an original, unworngeometry of the protrusions 118 depicted in dashed lines. In anembodiment, the direct write process, as described above, is used torepair airfoil shroud sections 50 that have worn protrusions 114. Anappropriate material, compatible with the coating material 58, isdeposited upon the worn geometry of the protrusions 114 of the coating58 via a suitable direct write tool 120, guided in an indicateddirection, for example, such as to build upon the worn protrusions 114to provide the original, unworn geometry of the protrusions 118.Subsequent to depositing the compatible material, an appropriateconsolidation tool 124 applies the appropriate consolidation species tothe deposited material to cure the material, thereby providing arepaired section 50 having the unworn geometry of the protrusions 118with suitable material characteristics for use within the turbine.

Referring now to FIG. 5 (in conjunction with FIGS. 1 through 4), aflowchart 130 of process steps of a method of forming the pattern 62comprising the plurality of recesses 66 and the plurality of protrusions70 within the coating 58 disposed upon the base 54 of the turbinecomponent 50 is depicted.

The method begins at Step 134 with selecting the turbine component 50,such as the airfoil shroud section 50 that includes the coating 58 forincorporation of the pattern 62. The method continues at Step 138 bysimultaneously dissolving a first plurality of portions of the coating58 disposed upon the selected turbine component 50. As used herein, theterm “simultaneously dissolving” refers to a process where somedissolving of the plurality of portions of the coating occur at the sametime, but does not require that all of the desired dissolving of theplurality of portions is initiated and completed in the exact same timeframe. As a result of the simultaneous dissolving of the first pluralityof portions of the coating 58, the plurality of recesses 66 of thepattern 62 are thereby defined. In an embodiment, a plurality ofcomponents 50 are selected, and the first plurality of portions uponeach component 50 of the plurality of components 50 are dissolvedsimultaneously, thereby providing an increased productivity. In anembodiment, the method further includes applying the mask 78 upon asecond plurality of portions of the coating 58, which correspond to theprotrusions 70.

The mask 78 may be formed via the lithographic process, which includescleaning the surface 64 of the coating 58 upon which the mask 78 will beapplied, applying the photoresistant material to the cleaned surface 64,and disposing the cover 82 having openings 84 that correspond to ageometry of the mask 78 (to be disposed upon the second plurality ofportions of the coating 58) between the energy source 86 and thephotoresistant material. In response to exposing the photoresistantmaterial to energy from the source 86 through the openings 84, thephotoresistant material is cured. Following removing uncuredphotoresistant material, the mask 78 is defined by the remaining curedphotoresistant material.

The mask 78 may also be formed by the direct write process, whichincludes cleaning the surface 64 of the coating 58 upon which the mask78 will be applied, and depositing the material of the mask 78 in theform of particles suspended within the fluid medium directly upon thecoating 58 via the robotic guidance control at the desired mask location78. The direct write process further includes applying the species, suchas heat for example, to cure the deposited mask 78 material, and therebydefine the mask 78 deposited upon the coating 58.

In one embodiment, the dissolving of the first plurality of portions ofthe coating 58 includes selecting the etchant to chemically dissolve thecoating 58 and exposing the coating 58 and the chemically resistant mask78 to the etchant. Accordingly, the chemically resistant mask 78prevents the dissolving of the coating 58 where the mask is applied andthereby defines the plurality of protrusions 70 of the pattern 58.

In another embodiment, using the ECM system 90, the dissolving of thefirst plurality of portions of the coating 58 includes applying theelectric potential via the power supply 94 to the coating 58 and thecathode (tool 102). The electrolyte 98 is conductive, and permits theflow of current between the cathode (tool 102) and coating 58.

One embodiment of the ECM system 90 utilizes the mask 78 as theelectrically insulating mask 78 to prevent passing of the charge throughthe coating 58, which prevents dissolving (at the second plurality ofportions) of the coating 58 upon which the mask 78 is disposed, therebydefining the plurality of protrusions 70 of the pattern 62.

Another embodiment of the ECM system 90 utilizes the cathode (tool 102)including the plurality of protrusions 111 in a pattern that defines theplurality of recesses 66. The tool 102 is disposed such that theplurality of protrusions 111 on the tool 102 correspond to the desiredlocation of the plurality of recesses 66 in the coating.

Repair of the used shroud section 50 may be accomplished via the directwrite process, which includes selecting the material for depositing uponthe coating 58, depositing the material upon one or more wornprotrusions 114 of the pattern 62, and applying the appropriate speciesto the deposited material to cure, or consolidate the depositedmaterial, thereby defining the geometry of unworn protrusions 118 andrepairing the worn section 50.

While an embodiment of the invention has been described employing a mask78 produced by lithography using a negative photoresist that cures inresponse to exposure to energy, it will be appreciated that the scope ofthe invention is not so limited, and that the invention will also applyto lithography that may use a positive photoresist, such that exposureto energy renders the photoresist soluble, for example.

As disclosed, some embodiments of the invention may include some of thefollowing advantages: an ability to reduce a cycle time forincorporating patterns into the surface of turbine airfoil shroudsections; an ability to produce a pattern within an airfoil shroudsection surface having resolution of 10 microns; an ability to reduce anoverall cost of an airfoil shroud section including a patterned surface;and an ability to repair an airfoil shroud section patterned surfacewithout removing any of the coating.

While the invention has been described with reference to exemplaryembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best oronly mode contemplated for carrying out this invention, but that theinvention will include all embodiments falling within the scope of theappended claims. Also, in the drawings and the description, there havebeen disclosed exemplary embodiments of the invention and, althoughspecific terms may have been employed, they are unless otherwise statedused in a generic and descriptive sense only and not for purposes oflimitation, the scope of the invention therefore not being so limited.Moreover, the use of the terms first, second, etc. do not denote anyorder or importance, but rather the terms first, second, etc. are usedto distinguish one element from another. Furthermore, the use of theterms a, an, etc. do not denote a limitation of quantity, but ratherdenote the presence of at least one of the referenced item.

1. A method of forming a pattern comprising a plurality of recesseswithin a turbine component, the method comprising: simultaneouslydissolving a plurality of portions of a selected section of the turbinecomponent, thereby defining the plurality of recesses of the pattern. 2.The method of claim 1, wherein: the selected section of the turbinecomponent comprises a plurality of selected sections of a plurality ofturbine components; and the step of simultaneously dissolving comprisessimultaneously dissolving the plurality of portions of each of theplurality of selected sections.
 3. The method of claim 1, wherein theplurality of portions is a first plurality of portions, the methodfurther comprising: applying a mask upon a second plurality of portionsof the selected section of the turbine component.
 4. The method of claim3, wherein the step of dissolving comprises: applying an electricpotential via a power supply to the turbine component and to anelectrode; and permitting a flow of current between the electrode andthe turbine component through an electrolyte.
 5. A method of forming apattern comprising a plurality of recesses within a coating disposedupon a turbine component, the method comprising: simultaneouslydissolving a plurality of portions of the coating disposed upon aselected section of the turbine component, thereby defining theplurality of recesses of the pattern.
 6. The method of claim 5, wherein:the step of simultaneously dissolving comprises simultaneouslydissolving a plurality of portions of the coating disposed upon aselected airfoil shroud, at least one of the coating and the airfoilshroud comprising a concave curvature.
 7. The method of claim 5,wherein: the selected section of the turbine component comprises aplurality of selected sections of a plurality of turbine components; andthe step of simultaneously dissolving comprises simultaneouslydissolving the plurality of portions of the coating disposed upon eachof the plurality of selected sections.
 8. The method of claim 5, whereinthe coating comprises at least one of nickel, cobalt, chromium,aluminum, yttrium, rhenium, rhodium, ruthenium, palladium, platinum,niobium, molybdenum, silicon, hafnium, iron, manganese, gadolinium,lanthanum, and alloys thereof.
 9. The method of claim 5, wherein theplurality of portions is a first plurality of portions, the methodfurther comprising: applying a mask upon a second plurality of portionsof the coating.
 10. The method of claim 9, wherein: the step ofdissolving comprises: selecting an etchant to dissolve the coating; andexposing the coating and the mask to the etchant; the step of applyingcomprises applying a mask that is chemically resistant to the etchant;and the method further comprises preventing dissolving of the secondplurality of portions of the coating, thereby defining a plurality ofprotrusions of the pattern.
 11. The method of claim 10, wherein the stepof selecting an etchant comprises selecting at least one of hydrofluoricacid, sulfuric acid, nitric acid, and combinations thereof.
 12. Themethod of claim 9, wherein the step of dissolving comprises: applying anelectric potential via a power supply to the coating and an electrode;and permitting a flow of current between the electrode and the coatingthrough an electrolyte.
 13. The method of claim 12, wherein the step ofapplying an electric potential comprises applying a pulsed DC electricpotential.
 14. The method of claim 13, the step of applying a pulsed DCelectric potential comprises applying alternating cathodic and anodicbiased pulses.
 15. The method of claim 12, wherein the electrolytecomprises at least one of: hydrofluoric silicate; ammoniumfluorosilicate; fluorosilic acid; an aqueous solution of at least oneof: sodium chloride; sodium nitrate; and sodium bromide; andcombinations thereof.
 16. The method of claim 12, wherein: the step ofapplying a mask comprises applying an electrically insulating mask; andthe method further comprises preventing dissolving of the secondplurality of portions of the coating, thereby defining a plurality ofprotrusions of the pattern.
 17. The method of claim 9, wherein the stepof applying comprises: cleaning a surface of the coating; depositing amask material directly upon the second plurality of portions of thecoating; and applying an activator to cure the deposited mask material,thereby defining the mask disposed upon the second plurality of portionsof the coating.
 18. The method of claim 17, wherein the depositingcomprises guiding a direct write tool via robotic control.
 19. Themethod of claim 5, further comprising: positioning an electrodecomprising a plurality of protrusions in a pattern defining theplurality of recesses such that the plurality of protrusions aredisposed corresponding to a desired location of the plurality ofrecesses; wherein the step of simultaneously dissolving comprises:applying an electric potential via a power supply to the coating and theelectrode; and permitting a flow of current between the electrode andthe coating through an electrolyte.
 20. The method of claim 19, whereinthe step of applying comprises applying a pulsed DC electric potential.21. The method of claim 5, further comprising: selecting a material fordepositing upon the coating; depositing the material upon the coating todefine one or more protrusions of the pattern; and applying anappropriate activator to consolidate the deposited material.